In the loading and off-loading of railway cargo cars, it is desirable to seal the area between terminal dock and/or shelter against inclement weather. Accordingly, the present invention is adapted to provide at a given warehouse or building dock, a protective unit that presents a weather-tight seal when extended from the dock against the open sliding door or side of the car. It is desirable that such a dock shelter not only permit complete and unobstructed rail car access, but also provide outstanding weather protection. The shelter herein is mounted along the outer perimeter of the dock opening of the terminal building warehouse. It is imperative that such a shelter permit free access to the rail car and that its gap closure be protected upon its sides and bottom during loading and unloading. The car should also be sealed by a head curtain above the shelter components. More specifically, the invention is a rail shelter which may be fitted to existing exterior dock walls for loading and off-loading. The unit is sufficiently versatile to accommodate a rail car which may be somewhat out of position, relative to a dock center as defined by the building construction. The dock center is conventionally determined by door jambs which are operatively disposed, defining the door opening of the building. Likewise, the shelter protection should continue its effectiveness despite rocking motions of the car when loaded and unloaded.